DC/DC converters, including buck-boost converters, may be used as drivers for loads with specific current and/or voltage requirements, such as chains of light-emitting diodes (LEDs). The light intensity of an LED chain is controlled by the amount of current flowing through it. Generally, a closed loop current generator may be used to keep the current constant. For lighting with a high current load, switched-mode controllers may be used. In applications that demand high efficiency and high flexibility, such as in some automotive lighting applications, a synchronous buck-boost DC/DC converter topology may be used.
Some applications in automotive lighting or other applications involve a single LED chain made up of a number of LEDs. The number may vary depending on the specific application. One or more of the LEDs can be bypassed at times, temporarily reducing the length of the LED chain. A DC/DC converter may control the current flowing through the LED chain as different numbers of the LEDs in the chain are used, while the output voltage is set by the number and the forward voltage of the LEDs that compose the chain.